A multiple-pulse emplacement model for the Shonkin Sag laccolith, Montana, USA

dc.contributor.author Ruggles, Claire
dc.contributor.author Morgan, Sven
dc.contributor.author Reber, Jacqueline
dc.contributor.department Geological and Atmospheric Sciences
dc.date 2021-06-23T19:39:44.000
dc.date.accessioned 2021-08-14T08:02:52Z
dc.date.available 2021-08-14T08:02:52Z
dc.date.copyright Fri Jan 01 00:00:00 UTC 2021
dc.date.embargo 2023-08-01
dc.date.issued 2021-08-01
dc.description.abstract <p>The Shonkin Sag laccolith (Montana) is a differentiated mafic hypabyssal intrusion that was concordantly emplaced into undeformed sandstones. Erosional processes have produced a cross-section-like exposure of the laccolith, revealing its base, roof, and eastern contact, where it transitions to fringing sills. We present evidence for a multi-pulse emplacement model for the Shonkin Sag laccolith by showing that the rapidly cooled margin of the laccolith and fringing sills preserve features formed during emplacement. These features include internal contacts associated with variably deformed zones at the margin of the laccolith and normal and thrust faults within the surrounding sedimentary rocks. Bulk magnetic susceptibility measurements, anisotropy of magnetic susceptibility and thin section analyses support evidence for strain accumulation in pulses. Thermal models suggest that the pulses emplaced over ~3 years, while total cooling and differentiation of the laccolith to the solidus occurred over ~21 years. From these results, a three-stage emplacement model was determined. The model provides insight into ground deformation and associated hazards caused by the rapid emplacement of shallow magma bodies similar in size to the Shonkin Sag laccolith, such as the 1980 Mt. St. Helens cryptodome and the 2011 Cordón Caulle laccolith.</p>
dc.description.comments <p>This is a manuscript of an article published as Ruggles, Claire E., Sven Morgan, and Jacqueline E. Reber. "A multiple-pulse emplacement model for the Shonkin Sag laccolith, Montana, USA." <em>Journal of Structural Geology</em> 149 (2021): 104378. doi:<a href="https://doi.org/10.1016/j.jsg.2021.104378" target="_blank" title="Persistent link using digital object identifier">10.1016/j.jsg.2021.104378</a>.</p>
dc.format.mimetype application/pdf
dc.identifier archive/lib.dr.iastate.edu/ge_at_pubs/363/
dc.identifier.articleid 1372
dc.identifier.contextkey 23489706
dc.identifier.s3bucket isulib-bepress-aws-west
dc.identifier.submissionpath ge_at_pubs/363
dc.identifier.uri https://dr.lib.iastate.edu/handle/20.500.12876/qzoDGk2w
dc.language.iso en
dc.source.bitstream archive/lib.dr.iastate.edu/ge_at_pubs/363/2021_Reber_MultiplePulseManuscript.pdf|||Fri Jan 14 23:47:50 UTC 2022
dc.source.uri 10.1016/j.jsg.2021.104378
dc.subject.disciplines Geology
dc.subject.disciplines Tectonics and Structure
dc.subject.disciplines Volcanology
dc.subject.keywords Shonkin Sag laccolith MT
dc.subject.keywords Laccolith
dc.subject.keywords Sills
dc.subject.keywords Pluton emplacement
dc.subject.keywords Magmatic fabric analyses
dc.subject.keywords Thermal modeling
dc.title A multiple-pulse emplacement model for the Shonkin Sag laccolith, Montana, USA
dc.type article
dc.type.genre article
dspace.entity.type Publication
relation.isAuthorOfPublication 5ee7cf94-4acc-41e7-b521-585d50f69510
relation.isOrgUnitOfPublication 29272786-4c4a-4d63-98d6-e7b6d6730c45
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